Re: [PATCH RFC v2 00/10] Introduce Signature feature

[Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 11/4/2013 8:41 PM, Nicholas A. Bellinger wrote:
> On Sat, 2013-11-02 at 14:57 -0700, Bart Van Assche wrote:
>> On 1/11/2013 18:36, Nicholas A. Bellinger wrote:
>>> On Fri, 2013-11-01 at 08:03 -0700, Bart Van Assche wrote:
>>>> On 31/10/2013 5:24, Sagi Grimberg wrote:
>>>>> In T10-DIF, when a series of 512-byte data blocks are transferred, each
>>>>> block is followed by an 8-byte guard. The guard consists of CRC that
>>>>> protects the integrity of the data in the block, and some other tags
>>>>> that protects against mis-directed IOs.
>>>> Shouldn't that read "logical block length divided by 2**(protection
>>>> interval exponent)" instead of "512" ? From the SPC-4 FORMAT UNIT
>>>> section:
>>> Why should the protection interval in FORMAT_UNIT be mentioned when it's
>>> not supported by the hardware, nor by drivers/scsi/sd_dif.c itself..?
>> Hello Nick,
>>
>> My understanding is that this patch series is not only intended for
>> initiator drivers but also for target drivers like ib_srpt and ib_isert.
>> As you know target drivers do not restrict the initiator operating
>> system to Linux. Although I do not know whether there are already
>> operating systems that support the "protection interval exponent",
> It's my understanding that Linux is still the only stack that supports
> DIF, so AFAICT no one is actually supporting this.
>
>>   I think it is a good idea to stay as close as possible to the terminology
>> of the SPC-4 standard.
>>
> No, in this context it only adds pointless misdirection because 1) The
> hardware in question doesn't support it, and 2) Linux itself doesn't
> support it.

I think that Bart is suggesting renaming block_size as pi_interval in 
ib_sig_domain.
I tend to agree since even if support for that does not exist yet, it 
might be in the future.
I think it is not a misdirection because it does represent the 
protection information interval.

> --nab
>

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